Conventionally, as this type of relief valve, a relief valve is known in which a valve member and an elastic member are accommodated in a hollow room formed in a center portion of a bolt-type valve body and in which a valve hole is provided in a tip end surface and a discharge hole is provided in a base end surface. When this relief valve is attached to, for example, a car air conditioner, and the pressure of a fluid (specifically, a coolant) is abnormally increased, the valve hole is opened, and thus part of the fluid is discharged from the discharge hole to the outside (see, for example, patent document 1).